Buttonhole-sewing machine



Oct. 1, 1929. A. F. CARLSON 1,729,995

BUTTONHOLB SEWING MACHINE Filed Sept. 17. 1927 s Sheets-Sheet 1 ln'venTor.

Axel F. Carlson byJgm/wt ATT Oct. 1, 1929. A. F. CARLSON 1,729,995

BUTTONHOLE SEWING MACHINE Filed Sept. 17, 1927 3 Sheets-Sheet 2 Flgfi. 27 Hindi-11: 1.!

I lnv'enror.

Axel F Carlson Anya Oct. 1, 1929. A. F. CARLSON BUTTONHOLE SEWING MACHINE Filed Sept. 17, 1927 3 Sheets- Sheet lnvenff. Axel Ficarlson WWW m Patented Oct. 1, 1929 warren srares rarenr oFricE AXEL F. CARLSON, OF CAMBRIDGE, MASSACHUSETTS, ASSIGNOR TO REECE BUT- TON HOLE MACHINE COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MAINE BUTTONI-IOLE-SEWING MACHINE Application filed September 17, 1927. Serial .\To. f220,106.

This invention relates to a two-thread buttonhole sewing machine of the rotary hook type, that is, a buttonhole sewing machine in which the under thread is taken from a bobbin and a rotary hook is employed for taking the loops of the upper or needle thread'and casting them about the bobbin to interlock the upper and under threads.

The principal object of the present invention is to provide a sewing machine of this type with novel means by which the purl of the buttonhole, or the point of interlocking between the upper and under threads, may be located on theupper side of the work.

In the operation of the ordinary twothread rotary hook type of buttonhole sewing machine the purl of the buttonhole is located on the under side of the work and since the I purl of the buttonhole is usually located on the front face of the work it has been the custom to place the work in a buttonhole sewing machine of this type bottom side up or with the front face down. For some reasons it is more desirable to have the work in the machine with the front face up or exposed to view and my invention makes this possible by providing means for placing the purl of the buttonhole on the upperside of the work. I accomplish this end herein by providing a novel means for pulling off a length of bobbin or under thread from thebobbin during the formation of each stitch and before the stitch is tightened, the amount so pulled off being sufficient so that when the stitch is tightened by the action of the take-up in pulling backwardly on the needle thread the. loop of bobbin thread will be drawn up through the work and the point of interlocking between the needle and bobbinthread will be on the upper surface of the work.

My invention is adaptable for any buttonhole sewing machine having a rotary hook although for illustrative purposes I have shown it as embodied in a rotary hook buttonhole sewing machine of the type illustrated in United States Patents No. 1,343,278, June 15th, 1920, No. 1,424,851, August 8th, 1922 and No. 1,478,760, December 25th, 1928. However, since the present invention concerns merely the manner of handling the up per and under thread to produce the purl on the'upper face of the work I have not deemed it necessary to illustrate a complete sewing machine herein but have contented myself with showing a suflicient portion of a sewing machine to enable the invention to be properly understood. 7 i

In the drawings, Fig. 1 is a fragmentary front view of a rotary hook buttonhole sew lng machine having my improvements applied thereto;

Fig. 2 is an enlarged fragmentary perspective view illustrative of the character of the stitch formed by my improvements;

, Fig. 3 is an enlarged fragmentary front view of the under thread mechanism showing the pull-off operating'on the bobbin thread;

F 4 is a section on the line 44, Fig. 8

Fig. 5 is a fragmentary front view of the under thread mechanism;

Figs. 6 and 7 are enlarged diagrammatic views showing different stages in the formation of the stitch. i

In the drawings 1 indicates a portion of the frame of a two-thread rotary'hook buttonhole sewing machine, said frame being provided with a head portion 2 in which reciprocates the usual needle bar 3 carrying the upper needle 4 by which the upper or needle thread 5' is controlled. The needle bar is 6 in a needle carrier 7 which has a lateral ogging movement as usual in sewing ma' chines 'of this type so that the alternate thrusts of the needle are at the slit of the buttonhole and the other thrusts are through the work at a distance from the slit. The under thread, which is indicated at 8, is taken from a suitable bobbin 9 which is supported in a bobbin case 10, the bobbin case having associated therewith a rotary hook 11 which is rotated from a suitable rotary shaft 12.

The parts thus far described are or may be all as usualin rotary hook buttonhole sewing machines. a

At each thrust of the needle 4 the needle thread 5 is carried through the work 13 and as the needle begins to rise it throws out a loop 14 which is caught by the hook 11 and locked with the bobbin thread 8. As the needle is retracted from the work the upper thread 5 is acted on by a vibrating take-up arm 29 which takes up slack in the needle thread and tightens the stitch.

It will be understood, of course, that the needle is given a jogging movement so that alternate thrusts will be at the buttonhole slit and the other thrusts will be through the work at a distance back of the slit.

' In accordance with my present invention I provide means for drawing off a length of bobbin thread from the supply during the formation of each stitch so that the length of bobbin thread leading from the bobbin to the work 13 will be somewhat slack at the time that the loop 14 of needle thread is cast about the bobbin. When the stitch is tightened by the take-up mechanism the backward pull on the needle thread 5 will take up the slack in the bobbin thread 8 and in so doing will draw the portion of the bobbin thread with which the needle thread is interlocked up through the goods and to the upper face thereof. This is perhaps best illustrated in Figs. 2, 6 and 7.

In Fig. 6 the needle {1 has just completed its penetrating thrust through the work 13 and at this time the length of bobbin thread leading from the work to the bobbin 9 is acted on'by a pull-01f finger 15 which pulls off a length of the bobbin thread 8 from thebobbin 9 thus producing the slack indicated by the portion 16 in Fig. 6.

Fig. 7 illustrates the position of the parts after the needle loop 14: has been cast about the bobbin and when the needle 4 is being raised and this shows the slack which exists in the bobbin thread. Asthe needle is'completely retracted the take-up acts to take up slack in the needle thread and to'tighten the stitch and in so doing the needle loop 1 1 is pulled up through the work 13 and at the same'time the portion of the bobbin thread with which the needle thread is interlocked is drawn up through the work to form a loop 17. Hence by pulling off the extra length of bobbin thread for each stitch the points where the upper and under threads 5 and 8 interlock will be located onthe upper face of the work as seen in Fig. 2, the complete buttonhole stitch presenting loops 17 of under thread which appear on thetop side of the work and with which the upper thread 5 is interlocked, the alternate loops being located at the center line of the buttonhole and the other loops being drawn through the work at a distance back from said center line. WVhen the buttonhole'is completed and cut (the cutting of the buttonhole frequently be ing performed -after the buttonhole is stitched) the loops 17 along the center line will pass around the edge 18 of the buttonhole slit as shown in Fig. 2.

The pull-off arm 15 may be operated in any appropriate way. As herein shown it is mounted on a rock shaft 19 journalled in suitable bearings 20 carried by the frame 1 and actuated from a cam or eccentric on the shaft 12. The rock shaft 19 has a crank arm 21 rigid therewith to which is pivoted an arm 22 of an eccentric strap 28, the latter encircling an eccentric 24 fast on the shaft 12. The arm 21 is shown as having a slot 25 to permit of adjustment of the point of connection between said arm and the eccentric arm '22 by which adjustment the amplitude of swinging movement of the pulloff arm 15 may be determined. This pull-off arm 15 is provided on its end with a hook 26 which is situated so that upon each oscillation of the arm 15 the hook will engage the length of under thread 8 which lies exposed on the front of the bobbin case. Said bobbin case is formed with a guiding projection 27 under which the-under thread 8 passes, said thread normally extending from the projection directly to the tension device 28 on the bobbin case as indicated by dotted lines in Fig. 6 and in full lines Figs. 1 and 5.

As the pull-01f arm 15 swings from its lowered position shown in Fig. 5 to its upper position shown in Fig.3 the hook will engage the portion of the underthread lying between the guiding projection 27 and the bobbin tension 28 and will draw off a length of bobbin thread through the tension. This drawing off of the length of bobbin thread occurs while the needle is in the workand, therefore, while the previous stitch is locked so that the pull of the pull-0E arm 15 on the under thread 8 will draw under thread from the bobbin through the tension rather than pull the last-formed stitch down through the work.

The tightening of the stitch is accom plished inusual wa by the operation of the take-up arm 29 w ich acts to pull backwardly on the needle thread when the needle has been withdrawn from the workthereby to pull said thread taut and as stated above since the bobbin thread is slack at this time the tightening of the stitch resultsin pulling a loop 17 of the. bobbin thread to the upper face of the work.

This invention, therefore, provides a simple device applicable to any rotary hook sewing machine and by which the point of interlock ing between the upper thread and the under thread may be drawn to the upper face of the work therebyplacing thepurl of the buttonhole on said face.

I claim:

1. A two-thread sewing machine comprising a needle carrying upper thread, a bobbin case, a bobbin therein carrying under thread, said bobbin case having a thread-guiding projection over which the thread is led to the. work, a rotary hook for casting loops of needle thread about the bobbin,'a swinging pull-oil arm situated to engage the under thread on the supply side of the projection and to pull off a suiiicient length of under thread so that when the stitch is tightened the interlocking of the upper and under threads will be pulled through to the upper side of the work.

2. A two-thread sewing machine comprising a needle carrying upper thread, a bobbin case, a bobbin therein carrying under thread, a tension for the under thread, said bobbin case having a thread-guiding projection which engages the under thread between the tension and the work, a rotary hook for casting loops of needle thread about the bobbin, and a pull-ofi device operating on said under thread between the tension and the threadguiding projection.

3. A twothread sewing machine comprising a needle carrying upper thread, a bobbin case, a bobbin therein carrying under thread, a tension tor the under thread, a threadguiding projection carried by the bobbin case and engaging the thread between the ten sion and the work, a rotary hook for casting loops of needle thread about the bobbin, a vertically-swinging pull-oft arm having a hooked end adapted to engage the under thread between the tension and the threadguiding projection and to pull off a length from the bobbin.

4. A two-thread sewing machine comprising a needle carrying upper thread, a bobbin case, a bobbin therein carrying under thread, a rotary hook for casting loops of needle thread about the bobbin, means to rotate the hook, a tension for the under thread, said bobbin case having a thread-guiding projection engaging the thread between the tension and the work, a rock shaft, a Vertically-swinging pull-oil arm mounted thereon and adapted to engage the under thread between the tension and the thread-guiding projection, and means to oscillate said arm from the hook-rotating means.

In testimony whereof, I have signed my name to this specification.

AXEL F. GARLSON. 

